SAN MATEO, California: A group of key US media giants have teamed to explore the legality of certain videos appearing on

The group, which includes News Corporation, NBC Universal and Viacom, is looking into whether YouTube might be liable for copyright-protected clips that are illegally uploaded to the site, alongside user-generated and authorized professional videos.

The move comes as no surprise following YouTube's agreement to acquisition by cash rich Google. If the deal is inked the internet search titan will become responsible for any potential copyright violations on the site.

In addition, and perhaps more relevantly, the media companies are holding separate negotiations to allow YouTube to carry their programming in return for a slice of advertising revenue.

Executives from Big Media hope their legal saber-rattling will soften YouTube to improve the terms it offers.

The video site, for its part, contends it has not broken copyright laws, because it immediately removes clips when rights holders complain about their inclusion.

TV network NBC, for example, has reportedly been asking for as many as 1,000 clips a month to be taken down, despite a deal inked earlier this year to make available promotional video clips for some of its popular programs.

Legal experts are divided on how much liability YouTube faces. Some say it is covered by "safe harbors" in the Digital Millennium Copyright Act of 1998, under which web-hosting sites have to comply with "takedown" notices from copyright holders when they become aware of content uploaded without their permission.

But John Palfrey, an intellectual-property professor at Harvard Law School, argues that YouTube should not fall within the safe-harbor protections because it is deriving direct financial benefit from the infringement.

Data sourced from Wall Street Journal Online; additional content by WARC staff